Implement "Application instances manager"

src/app/qtlocalpeer/qtlockedfile_unix.cpp

@@ -0,0 +1,115 @@
+/****************************************************************************
+**
+** Copyright (C) 2013 Digia Plc and/or its subsidiary(-ies).
+** Contact: http://www.qt-project.org/legal
+**
+** This file is part of the Qt Solutions component.
+**
+** $QT_BEGIN_LICENSE:BSD$
+** You may use this file under the terms of the BSD license as follows:
+**
+** "Redistribution and use in source and binary forms, with or without
+** modification, are permitted provided that the following conditions are
+** met:
+**   * Redistributions of source code must retain the above copyright
+**     notice, this list of conditions and the following disclaimer.
+**   * Redistributions in binary form must reproduce the above copyright
+**     notice, this list of conditions and the following disclaimer in
+**     the documentation and/or other materials provided with the
+**     distribution.
+**   * Neither the name of Digia Plc and its Subsidiary(-ies) nor the names
+**     of its contributors may be used to endorse or promote products derived
+**     from this software without specific prior written permission.
+**
+**
+** THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+** "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+** LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+** A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+** OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+** SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+** LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+** DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+** THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+** (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+** OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE."
+**
+** $QT_END_LICENSE$
+**
+****************************************************************************/
+
+#include <string.h>
+#include <errno.h>
+#include <unistd.h>
+#include <fcntl.h>
+
+#include "qtlockedfile.h"
+
+bool QtLockedFile::lock(LockMode mode, bool block)
+{
+    if (!isOpen()) {
+        qWarning("QtLockedFile::lock(): file is not opened");
+        return false;
+    }
+ 
+    if (mode == NoLock)
+        return unlock();
+           
+    if (mode == m_lock_mode)
+        return true;
+
+    if (m_lock_mode != NoLock)
+        unlock();
+
+    struct flock fl;
+    fl.l_whence = SEEK_SET;
+    fl.l_start = 0;
+    fl.l_len = 0;
+    fl.l_type = (mode == ReadLock) ? F_RDLCK : F_WRLCK;
+    int cmd = block ? F_SETLKW : F_SETLK;
+    int ret = fcntl(handle(), cmd, &fl);
+    
+    if (ret == -1) {
+        if (errno != EINTR && errno != EAGAIN)
+            qWarning("QtLockedFile::lock(): fcntl: %s", strerror(errno));
+        return false;
+    }
+
+    
+    m_lock_mode = mode;
+    return true;
+}
+
+
+bool QtLockedFile::unlock()
+{
+    if (!isOpen()) {
+        qWarning("QtLockedFile::unlock(): file is not opened");
+        return false;
+    }
+
+    if (!isLocked())
+        return true;
+
+    struct flock fl;
+    fl.l_whence = SEEK_SET;
+    fl.l_start = 0;
+    fl.l_len = 0;
+    fl.l_type = F_UNLCK;
+    int ret = fcntl(handle(), F_SETLKW, &fl);
+    
+    if (ret == -1) {
+        qWarning("QtLockedFile::lock(): fcntl: %s", strerror(errno));
+        return false;
+    }
+    
+    m_lock_mode = NoLock;
+    return true;
+}
+
+QtLockedFile::~QtLockedFile()
+{
+    if (isOpen())
+        unlock();
+}
+